Cancer of the uterine cervix is the second most common cancer in women world-wide and is responsible for approximately 250,000 cancer deaths a year.
Cervical squamous cell carcinoma development is characterized by a sequence of premalignant lesions, so-called cervical intraepithelial neoplasia (CIN), which are graded 1 to 3, referring to mild dysplasia (CIN 1), moderate dysplasia (CIN 2) and severe dysplasia/carcinoma in situ (CIN 3), respectively. CIN 1 is also referred to as low grade squamous intraepithelial lesion (LSIL) and CIN 2 and CIN 3 together as high grade squamous intraepithelial lesion (HSIL) For cervical adenocarcinoma, adenocarcinoma in situ (ACIS) is an established precursor lesion. In principle, these premalignant lesions are reversible, although the more severe the lesion, the lower the chance of spontaneous regression. Cervical cancer is considered a preventable disease because the premalignant stages can be detected by exfoliative cytology and treated relatively easily when necessary, with only minor side effects. Cervical screening is aimed to early diagnose the high-grade premalignant (i.e., CIN 2/3 and adenocarcinoma in situ) and treatable cancerous lesions, thereby reducing the mortality of invasive cervical cancer. General medical practice comprises the treatment of all women with morphologically confirmed CIN 2, CIN 3 and adenocarcinoma in situ, in order to prevent the development of cervical cancer.
Over the past decade it has been well established that cervical carcinogenesis is initiated by an infection with high-risk human papillomavirus (hrHPV). Expression of the viral oncogenes E6 and E7, which disturb the p53 and Rb tumor suppressor pathways, respectively, has been shown to be essential for both the onset of oncogenesis and the maintenance of a malignant phenotype. Therefore, testing for hrHPV appeared as an attractive, primary screening tool. However, consistent with a multistep process of carcinogenesis, additional alterations in the host cell genome are required for progression of an hr-HPV infected cell to invasive cancer cell. Only a small proportion of women infected with high-risk HPV will develop high-grade premalignant cervical lesions (CIN 2/3) and, if left untreated, cervical cancer. In most women with premalignant cervical lesions the lesions regress spontaneously. Of the women who participate in population based screening about 5-6% have a positive hrHPV test (Bulkmans et al., Int J Cancer 2004, 110:94-101). However, only at maximum 20% of them (1% of the participating women) have ≧CIN 2/3. Therefore, primary screening by hrHPV testing will be accompanied with a substantial number of redundant follow-up procedures and unnecessary anxiety amongst women, unless markers can be applied to the cervical smears that allow stratification of hrHPV positive women for risk of ≧CIN 2/3 and ≧adenocarcinoma in situ.
A major challenge is to reduce the percentage of test positive women to those that have clinically meaningful lesions. One mode is to use cytology as a secondary (so-called triage) test for hrHPV positive women. Still, this leaves a substantial number of hrHPV positive women with normal cytology (3.5% of the women in the screening population), of which 10% have or acquire ≧CIN 3. Moreover, cytology is not an option for self-sampled cervico-vaginal specimens that can be taken at home, since these are not representative for the cytological status of the cervix (Brink et al., 2006, J. Clin. Microbiol. 44:2518-2523). Therefore, there is a need for supplementary or alternative triage tools to stratify hrHPV positive women into those with and without ≧CIN 2/3 and ≧adenocarcinoma in situ.